Obtaining samples of molten metal for laboratory analysis has been a problem confronting metallurgists for many years. In recent years efforts have been made to obtain the sample by immersing a sample taking and forming device into the bath of molten metal. U.S. Pat. No. 3,455,164 issued to G. P. Boyle discloses one such sampling device in which the sampler body consisted of two sections of a shell molding made from resin coated sand and cemented together. The purpose for using the resin coated sand was to permit gas to escape through the body of the mold. As set forth in the patent, the shell molding technique includes the step of baking to harden to give the mold mechanical strength. One of the problems associated with the shell molding step of baking to provide mechanical strength is that as the baking time and temperature are increased to improve the strength of the mold, the material loses its porosity and characteristic of permitting gas to pass therethrough. The baking step must then be at best a compromise situation between strength and porosity.
It has also been found that the mold constructed by the shell molding technique generates or releases gas when subjected to the temperature of molten iron or steel. Not only does this gas increase the total volume of gas to be vented by adding to the gases trapped in the mold cavity and those released from the metal as it cools, but it represents a possible source of contamination of the metal sample.
Another approach to a sampler design is disclosed in U.S. Pat. No. 3,557,624 issued to W. J. Collins showing a pin sampling device using a fibrous material such as steel wool to provide a venting of entrapped gases into a chamber of limited volume. Additionally the sampler utilizes a plurality of metallic cups to provide entrance passages for the sample. Because of the limited volume of the venting chamber there exists the possibility that there is not sufficient venting capacity. This possibility is particularly great where the sampler is used to obtain samples from a bath that has a high degree of superheat and thus liberates large quantities of gases as the metal cools. Additionally there exists in this design the possibility of contamination of the sample when the sample contacts the steel wool.
Applicant has discovered that the devices taught in the prior art have failed to provide a device that has sufficient dependability that it can be used under the wide variation of conditions existing throughout the molten metal industry. While the devices of the prior art might function properly with certain bath conditions, the same device might due to differences in temperatures and molten metal composition not perform satisfactorily when used with other molten metal baths. Furthermore, the devices of the prior art resulted in the possibility of contamination of the sample from the materials used to provide restricted venting.